Pressure charged diesel engines normally include a method for processing the air-fuel mixture leaking past the pistons from the combustion chambers, referred to as "blow-by gas". This processing generally includes exhausting the blow-by gas to the atmosphere which increases environmental concerns. However, the processing may include an air-oil separator for initially separating the oil from the blow-by gas so that the "cleaned" blow-by gas is introduced into the intake system through an air charging system, such as a turbocharger, for reburning in the combustion chambers. This requires that the air-oil separator be very efficient in order to remove a high percentage of the oil from the blow-by gas so that the turbocharger impeller will not become entrained with oil, lowering the efficiency of the turbocharger and, perhaps, ultimately leading to the failure of the turbocharger. Unfortunately, air-oil separators which are a complicated or expensive design may not ensure that the removal of oil will be sufficient to protect the turbocharger. Additionally, the use of the air-oil separators includes outside lines which can be damaged and add complexity and cost to the engine design.
An example of a blow-by scavenging system for a diesel engine is disclosed in U.S. Pat. No. 4,363,310 issued to Kelly W. Thurston on Dec. 14, 1982. In the preferred embodiment, the pistons of the engine are provided with blow-by storage chambers between the upper piston rings and a scavenging system to flush out blow-by gases from the storage chambers when the pistons are at or near their bottom positions. The scavenged blow-by gas is recirculated to the engine induction system or may be conducted directly to the associated combustion chambers. However, the scavenging system disclosed by Thurston will not capture the entire amount of blow-by as it passes the pistons. The portion of blow-by gas which is not captured in the scavenging system steadily accumulates within the crankcase making it necessary to, at some specified time interval, relieve the pressure therein.
The present invention includes a method of ventilating the blow-by gas within the crankcase at specified time intervals in the engine cycle and directing the blow-by gas to the combustion chamber directly without introduction through the air charging system. The present invention provides an inexpensive design for improved control of blow-by gas.